Method and apparatus for taking physical measurements in boreholes



June 3, 1947. s, KRASNOW 2,421,423

METHOD AND APPARATUS FOR TAKING PHYSICAL MEASUREMENTS IN BOREHOLES Original Filed Oct. 29, 1936 2 Sheets-Sheet l IZ F l5 /7 awe/who's June 3, 1947. 's KRASNOW 2,421,423

METHOD AND APPARATUS FOR TAKING PHYSICAL MEASUREMENTS IN BOREHOLES Original Filed Oct. 29, 19 56 2 Sheets-Sheet 2 Patented June 3, i947 EJNHTE METHOD AND APPARATUS FOR TAKING PHYSICAL MEASUREMENTS IN BORE- HOLES Shelley Krasnow, Arlington County, Va., assignor to Geophysical Development Corporation,

Washington, D. 0., a corporation of Delaware Original application October 29, 1936, Serial No. 108,312. Divided and this application February 15, 1943, Serial No. 475,944

8 Claims. 1

This invention relates to a method and app ratus for making physical measurementsin inaccessible locations, and has particular reference to a method and apparatus for making physical measurements in deep bore holes.

An object of the invention is to provide a method and apparatus such that aknowledge of physical conditions at a site may be'gained at a considerable distance from the sitewithout the intermediacy of any electric cables. In the particular application mentioned, a knowledge may be gained at the surface of the earth of physical conditions many thousands of feet below the surface.

A further object of the invention is to providean apparatus and method such that measurements of more than one physical quantity may be made in rapid succession.

A still further object of the invention is to provide an apparatus and method such that two or more physical quantities may be measured simultaneously.

Reference is had to the accompanying drawings in which:

Figure 1 is a, schematic view showing the apparatus applied to taking physical measurements in a bore hole.

Figure 2 shows a schematic view of the sound generator used for measuring temperature.

Y Figure3 shows a schematic view of a corresponding generator for measuring pressure.

Figure 4 shows a, schematic view of a corresponding generator for measuring electrical properties.

Figure 5 shows an enlarged view of the element sensitive to pressure, used in the generator shown in Figure 3, the section being taken across the lines l--I in Figure 3.

Figure 6 shows a partial schematic view of the circuit used in the generator shown in Figure 4.

Figure '7 shows a further schematic view of the circuit used in the generator shown in Figure 4.

Figure 8 shows/a schematic partial view of a generator for measuring inclination.

Figure 9 shows a schematic partial View of a generator for the simultaneous or successive measurement of temperature and pressure.

Figure 10 shows the wiring diagram of the circuit used in measurement of temperature.

Figure 11 shows the wiring diagram of the circuit used for measuring pressure.

Figure 12 shows schematically the arrangement for detecting vibrations.

Figure 13 shows a modulated wave form suit- 2 able for the simultaneous measurement of two physical quantities.

The measurement of certain physical quantities such as pressure and temperature in bore holes, has proved to be of great practical importance. A number of methods have been devised for obtaining these measurements. One

method, in common use, is to send down a cartridge containing an apparatus for recording graphically the change in physical conditions as the apparatus is lowered, or in a simpler form, to record the value of a physical quantity at a single depth. Another method much used is to convert the physical quantity being measured into an electrical quantity (if the quantity being measured is not itself, in fact, electrical) and by means of electric cables extending upward from the measuring element make possible the indirect measurement of the physical quantity at the surface.

A disadvantage of the first method named is that it does not permit a ready observation of the quantity being measured while the measurement is being taken. A disadvantage of the second method is that a, heavy and expensive electric cable must be used. In some bore holes, mud, salt water, and crude oil exist at difierent levels. The problem of providing a cable insulation which will withstand all of these, and at the same time be resistant to abrasion, is a dimcult one. Further still, the best conductors of electricity are not mechanically strong, so that a high strength wire must be twisted together with the electrical conductors. The additional weight provided by the strengthening wires and insulation is such as to make the cable very much heavier than the object lowered at its end, in the case of deep bore holes.

In the instant invention, the physical quantity being measured is converted into a mechanical vibration or into sound waves; the frequency of either of these varying as a known function of the physical quantity being measured. This can be done by providing a sound or mechanical vibration generator, which is lowered to the depth at which it is desired to take measurements. The frequency of the sound, or the frequency of the mechanical impulses is determined by the magtively rigid body such as the casing or drill-Pip in the bore hole. A device for detecting the sound or mechanical vibration, and for measuring its frequency, is placed at any convenient site. By the value oi the frequency obtained it is possible to deduce the magnitude of the physical quantity being measured.

Referring now in detail to the drawings, l is a cartridge containing the apparatus for generating sound or mechanical vibrations. 2 is a supporting member which may be a wire of high strength material. The member 2 makes contact with a feeler I3 after which it passes over a pulley 3 and is wound upon on a reel 4. The feeler i3 acts through the intermediacy of a vibration sensitive device, hereinafter more fully described, on a frequency measuring device I.

If the physical quantity measured is temperature, the apparatus shown in Figure 2 is used. Here a thermo-couple 8 is exposed to the temper ature in the well through a heat-conducting medium ill. The thermo-couple 9 is kept at a constant temperature and thus serves as the reference thermo-couple. Both of these couples are connected in series and also with the generator 1, the circuit employed in I being such that a change in applied E. M. F. will cause a change in frequency as will be later more fully described. A battery compartment l I serves to hold the batteries which provide the energy for the generator I. The electrical oscillations generated by the generator I are converted into mechanical or sound oscillations by means of a suitable loud speaker element 6. To the latter is fastened the end of the member 2. A diaphragm serves to allow the transmission of the vibrations through the walls of the housing i2, and at the same time prevent the flow of fluid into the housing.

Figure 3 shows an apparatus used for measuring pressure. In this a pressure sensitive element I5 is placed adjacent an outer wall of the cartridge I2. The variation in pressure will cause a change in electrical constants of the element l5. This change, acting on the electrical oscillator 41, will cause a change in the frequency of current transmitted to the loud speaker element 8.

Figure 4 shows an apparatus adapted for measuring the electrical properties of the material surrounding the bore hole. In the particular modification shown, the electrical resistivity is measured by means of the Wenner four-electrode method. The housing l2 is made of insulating material and four conducting rings, i9, 20, 2| and 22, are fastened to the outside of the housing. A current is maintained between the rings i9 and 22 as shown schematically in Figure 7. Here a battery 26 has one pole connected through the ballast resistance 31 to the ring 22, and has its other pole connected to the ring I9. The E. M. F. between rings 20 and 2|, resulting from the passage of the current, is applied to the oscillater I, as in the apparatus shown in Figure 10;

Figure 8 shows a. part view of an apparatus for measuring the inclination of a bore hole. Here the position of a pendulum 39 relative to a support 38 determines an electrical constant in the circuit of a generator such as l9. Thus a change in inclination will cause a change in frequency oi the oscillation emitted by the generator 19.

Figure 9 shows a part view of an apparatus for the simultaneous measurement of temperature and pressure. This is the equi alent of a combination of the elements shown in Figures 2 and 3. It is understood that the frequency change 4 be noted on the lowering of the cartridge in the bore hole, and the frequency due to the pressure measuring element noted on the raising of the cartridge. A time switch may be placed within the housing l2 so as to disconnect the elements 8 and 9 from circuit and connect the element l5 after a predetermined interval. In using such an apparatus, a predetermined interval long enough to allow lowering of the cartrid e would be chosen. Thus, after the cartridge was lowered to its desired depth, temperature measurements being taken on the way, the time switch would cause the connection of the pressure measuring element and on raising the cartridge pressure would be measured. As alternative to this, pressure and temperature may be measured simultaneously by the use of a modulated mechanical or sound oscillation as will be hereinafter more fully described.

Figure 10 shows a circuit diagram for the unit shown in Figure 2. Here 8 is the measuring and 9 the reference thermo-couple. 21 is a vacuum tube of conventional type. In series with its grid are the couples 8 and 9, a biasing battery 25 and balancing rheostat 26, in parallel therewith, and one end of the filament of the tube. A battery 28 serves to heat the filament, in a conventional fashion. In the plate circuit are the coil 30 of the transformer ii, the usual B battery 29, and one end of the filament of the tube. Another coil 34 of the transformer II, is connected between the grid of the vacuum tube 35, and one end of the filament of the same tube. Another coil 33 of the transformer Si, is connected between the plate of the tube. and the B battery 29*. A lead is connected from one pole of the B battery to one end of the illsment, in the conventional fashion. Another coil 32 of the transformer 3!, is connected directly to the loud speaker element 6. The operation of the apparatus is as follows: The E. M. F. generated by the diiference of temperature between thermo-couples 8 and 8. causes a change in the potential of the grid of the tube 21. This causes a corresponding and magnified change in the direct current flowing in the plate circuit of the tube and consequently in the coil 30 of the transformer 3|. This in turn causes a change in the flux in the core of the transformer 3|. The coils 33 and 34, tube 35, battery 29'- and battery 22 constitute a generator of electrical oscillations.

The frequency of the oscillations generated will be dependent on the saturation of the core of the transformer 3|. Thus a change in E. M. F. generated by thermo-couple I will cause a change in the frequency of the oscillations generated in the oscillatory circuit described above. The oscillations generated will be picked up by the coil 32 of the transformer 3i, and converted into mechanical oscillations by means of the loud speaker element 8.

The circuit shown in Figure 11 is that of the generators shown in Figures 3 and 8. It is seen that the circuit is that of a conventional vacuumtube oscillation generator, the frequency of the oscillations being made variable by the variable condenser I I. In the case of the measurement of pressure, a cell such as that shown in Figure 5 constitutes the element ii. In this a heavy metal plate I is kept separated from a thin metal diaphragm l8 by-means of an insulating ring II.

An increase in pressure will cause a deflection of the diaphragm I8 and thus bring portions of it closer to the plate It. If wires are connected due to the temperature measuring element may 16 p t v y to e Plate 8 n diaphragm ll.

the unit will function as a variable condenser.

It is understood that the member 18 forms part of the outer wall of the cartridges If and I2. In the case of the apparatus shown in Figure 8, the tilt of the pendulum 39 relative to its support 38 may be made to alter the capacity of a member IS in the circuit shown in Figure 11, and thus cause a change in generated frequency. As before, this electrical oscillation is converted into a mechanical one by means of the loud speaker element 6.

The means of detecting the oscillations is shown in Figure 12. Here the supporting member 2 is allowed to make frictional contact with a semi-flexible member 44, resting on a support 45. The member 44 may be made of metal. Between the member 44 and support 45 is placed a microphone element 46 of conventional type, which is in turn connected to an electrical frequency measuring apparatus shown schematically at M. In cases where it is desired to measure two physical quantities simultaneously, a modulated wave form is used as shown in Figure 13. Here, one frequency is determined by one of the quantities being measured, the other frequency being determined by the other quantity. Thus in the method of making simultaneous measurement of more than one physical quantity, there may first be generated a wave, causing the frequency of the wave to be altered as a known function of the magnitude of one physical quantity, of generating a second wave, and causing the frequency of the second wave to be altered as a known function of the magnitude of another physical quantity, superposing one wave upon the other to produce a modulated wave, conducting the modulated wave to a remote point, and measuring characteristics of the components of the modulated wave. Thus the simultaneous measurement of temperature and pressure, or temperature and electrical properties, or any other two quantities, may be made. This factor is of importance in cases where the taking of measurements involves the suspension of drilling activities. At such times the cost of maintaining the drilling equipment and crew idle may amount to serious proportions.

In cases where it is desired to measure electrical properties, the circuit shown in Figure is employed, the thermo-couples 8 and 9 being removed and the elements 20 and 2| shown in Figure 6 being substituted and being connected at the points in the circuit 23 and 24.

It is obvious that various changes may be made without departing from the scope and spirit of the invention. Thus the element I may be used to take measurements of temperature, pressure, and electrical properties, in deep bodies of water. By this means, salinity of ocean water may be conveniently measured at great depths. It is further obvious that the method may be used in meteorological work, where a balloon or kite is sent aloft carrying with its sound generators, the frequency of the emitted sound being made proportional to the physical quantity it is desired to measure. This sound may be conveyed to the earth either through a fine metal filament or through air. In the latter case any one of the numerous sensitive devices for detecting sounds in air may be used.

It is further obvious that different types of generators than that described may be used. Thus a vibrating reed may be used for the measurement of temperature, a means being employed to keep the reed vibrating, the natural frequency of the reed being altered by the temperature.

It is further obvious that the sound generated by the generator may be transmitted through the fiuid medium in which the generator is immersed. In many cases the cartridge with its enclosed generator will be immersed in liquid. This is particularly true of the modifications of the apparatus shown in Figures 3, 4, and 9. In such cases the sound or mechanical vibrations may be conducted upwards through the liquid, and may be detected and measured at the surface. Where a metallic casing or metallic drill stem exists in a bore-hole under investigation, either may be used to convey the sound or mechanical vibrations.

It is further obvious that the pick-up device for detecting the sound may be modified. Thus if a member such as 2 is used the wheel 3 may itself be made the pick-up by being mounted on suitably sensitive supports. Alternatively, a coil may surround the wire and the oscillation in the latter be detected by the magnetostrictive eifect.

It is further obvious that electric circuits other than those shown in Figures 10 and 11 may be used to generate the mechanical vibrations or sound.

It is further obvious that the frequency indicating apparatus I may be designed to furnish a continuous record of the frequency of the sound detected by the pick-up member I3.

This application is a division of application Serial No. 108,312, filed October 29, 1936, entitled Method and apparatus for taking physical measurements in boreholes.

I claim:

1. In an apparatus for investigation of electrical properties within a deep narrow borehole, a holder of narrow lateral dimensions adapted to be lowered into the said borehole, a system for generating oscillations mounted within said holder, electrodes mounted upon the exterior of the said holder, so as to be in conducting relationship to material within the borehole, means to impress an electro-motive force upon some of the said electrodes, means to sense the resulting electro-motive force in an electrode other than the first named electrodes, the saidsensing means being connected to the said other electrode and being adapted to modify the frequency generated by the said oscillator, means to transmit the said modified oscillations to the surface of the earth, 1

and means at the surface of the earth to receive and detect the said oscillations.

2. In an apparatus for the measurement'of intensity of radiant energy within a deep narrow borehole, a holder of narrow lateral dimensions adapted to be lowered to various depths within the said borehole, the said holder carrying a generator of oscillations, transmitting means, an electrical conductive element directly sensitive to the radiant energy adapted to have its electrical properties varied in relation to the intensity of radiant energy in its vicinity, the said "sensitive element being connected to the oscillator soas to modify a characteristic of the oscillations generated thereby in relation to the electrical properties of the said sensitive member, the transmitting means being connected to the oscillator and adapted to transmit the modified oscillations to the surface of the earth and means to receive and detect the said oscillations.

3. An apparatus as in claim 2, in which the characteristic modified is the frequency.

4. An apparatus as in claim 2 in which a direct current voltage is varied in proportion tojthe 7 intensity of the radiant energy, the oscillation characteristics being modified in proportion to the'said direct current voltage.

5. An apparatus as in claim 2 inwhich the element sensitive to radiant energy is connected to a direct current voltage source and a-means to modify the generated oscillations in proportion to a direct current voltage.

6. An apparatus as in claim 2 in which the oscillator operates continuously, independently of the element sensitive to radiant energy, but has the characteristics of the oscillations generated modified in accordance with the response from the said radiant energy sensitive element.

7. An apparatus as in claim 2 in which the output of the radiant energy sensitive element is a direct current voltage varied in proportion to the intensity of the radiant energy:

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,991,658 Clark Feb. 19, 1935 2,190,950 Potapenko Feb. 20, 1940 2,219,273 Scherbatskoy Oct. 22, 1940 2,225,668 Subkow Dec. 24, 1940 2,285,809 Davis June 9, 1942 

